From European Patent No. 0 683 862 an electromagnetically operable fuel injector is known whose armature is characterized in that the armature stop face facing the inner pole has a slightly wedge-shaped design in order to minimize or completely eliminate the hydraulic damping upon opening of the fuel injector and the hydraulic adhesion force after interruption of the current that energizes the solenoid coil. In addition, owing to suitable measures such as vapor deposition and nitration, the stop face of the armature is wear-resistant, so that the stop face has the same size during the entire service life of the fuel injector and the functioning method of the fuel injector is not impaired.
Disadvantageous in the fuel injector known from European Patent No. EP 0 683 862, in spite of the optimized armature stop face, is primarily the hydraulic damping force still acting in the working gap upon pull-up of the armature. If an excitation current is applied to the solenoid coil, the armature moves in the direction of the inner pole and, in so doing, displaces the fuel present between the inner pole and the armature. Because of frictional and inertia effects, a local pressure field builds up which produces a hydraulic force on the armature stop face that acts counter to the moving direction of the armature. The opening and fuel-metering times of the fuel injector are thereby prolonged.